Prior art devices for heating and cooking of foodstuff are known. However, such devices are typically limited in the volume of the foodstuff which may be heated or cooked thereby, thus precluding commercial applications of such prior art devices. Prior art commercial ovens, which have rack guided tracks for stackability of a large number of pans, are thus convection ovens, wherein a slow convection heating process is utilized.
Moreover, the known prior art devices utilize oscillating circuits requiring power tubes which are specially designed therefor. The prior art oscillating circuits generally provide a substantially fixed distribution of voltage and power within the heating cavity. Thus, longer heating or cooking times are required for heating or cooking greater volumes of foodstuff. Further, the prior art devices operate at frequencies which are strongly dependent on the characteristics of the foodstuff being cooked.
Additionally, while prior art high frequency cooking cavities are known to include a vertical stacking facility, thus permitting heating of multiple levels of food within a single cavity, only a single pair of electrodes is provided for transferring the electromagnetic energy to the heating (or cooking) cavity. Thus, when use is made of the different numbers of available cooking levels, the quantity of energy delivered to each food product is reduced and longer heating or cooking times are required.
There is thus a need in the prior art for high frequency dielectric heating devices capable of heating and cooking commercial quantities of foodstuff. There is more particularly a need in the prior art for high frequency heating devices capable of heating large quantities of foodstuff without experiencing a resultant lengthening in the necessary heating time. There is a specific need in the prior art for multilevel cooking structures to facilitate performance of such operations, wherein the use of such plural levels for the heating of foodstuff does not result in a reduction in the quantities of energy delivered per unit time to the various foodstuffs being cooked.
There is a further need in the prior art to provide a high frequency, dielectric heating apparatus, having an increased efficiency of energy transfer between the power tube of the oscillating circuit and the foodstuff, where dielectric losses generate a desired heat level.